1. Field of the Invention
The present invention relates to dry, granular bleach compositions comprising an organic peroxycarboxylic acid as the active bleaching agent, and to a process for making such dry, granular bleach compositions.
2. Description of the Related Art
Granular bleach compositions which comprise an organic peroxycarboxylic acid as the active bleaching agent are known in the art. Thus, Lund et al. disclose in their U.S. Pat. No. 3,494,787 dry granular compositions of diperphthalic acid, encased in a protective coating of hydrated salts. These salts are slightly acidic or essentially neutral. These dry granular compositions are prepared by feeding an aqueous dispersion of the diperphthalic acid into a fluidized bed of incompletely or non-hydrated salt particles. These compositions exhibit a reduced tendency to detonate or explode.
Similarly, Nielsen in U.S. Pat. No. 3,770,816 discloses non-detonable granular bleach compositions comprising diperisophthalic acid and an inert hydrated salt. These compositions are prepared in granular form by admixing unhydrated or partially hydrated salts with e.g. a water-wet filter cake comprising the diperisophthalic acid in such proportion that the salt takes up the water in the filter cake to form a hydrate. In doing so, granular compositions are obtained. The salts used are slightly acidic or essentially neutral.
More recently, attention has been focused on other, aliphatic organic peroxyacids such as diperoxydodecanedioic acid (DPDA) as a suitable bleaching agent, e.g. for inclusion in detergent and cleaning compositions. Like the aforesaid diperphthalic acids, such aliphatic organic peroxyacids can decompose exothermally nd can detonate or explode. In U.S. Pat. No. 4,091,544 (Hutchins), it is proposed to prepare e.g. DPDA-granules by forming a water-wet mixture of DPDA with a hydratable salt above the hydration temperature, comminuting said mixture, cooling the comminuted mixture to below the hydration temperature and subsequently drying the mixture to remove free water and water of hydration. The hydratable salts include sodium sulphate, calcium bromide, ferric bromide, ferric chloride, ferric nitrate, lithium bromide, sodium acetate, sodium arsenate, sodium perborate, sodium phosphite, sodium acid phosphite and stannous chloride. In U.S. Pat. No. 4,100,095 (Hutchins et al.), granular DPDA-compositions are described which contain, as exotherm control agents, a non-hydrated salt which chemically decomposes to give off water below the decomposition temperature of DPDA.